U.S. patent application number 12/444269 was filed with the patent office on 2009-12-17 for milling tool and method, in particular for milling composite materials.
Invention is credited to Aldo Falchero, Vincenzo Galota, Guido Mancina.
Application Number | 20090311055 12/444269 |
Document ID | / |
Family ID | 39092794 |
Filed Date | 2009-12-17 |
United States Patent
Application |
20090311055 |
Kind Code |
A1 |
Galota; Vincenzo ; et
al. |
December 17, 2009 |
MILLING TOOL AND METHOD, IN PARTICULAR FOR MILLING COMPOSITE
MATERIALS
Abstract
The tool (1) according to the invention is equipped with cutting
inserts (5) made of polycrystalline diamond and with washing
channels cooling the tool from the inside and discharging, through
outlet holes (15), jets of compressed air that remove the highly
abrasive powders produced during machining from the cutting areas.
In this manner, the tool undergoes less abrasion and anyway it can
be sufficiently cooled. The particular choice of the material of
the cutting inserts makes the tool more abrasion resistant, while
conferring it in the whole a longer operating life. The invention
also concerns a method of milling composite materials.
Inventors: |
Galota; Vincenzo; (Torino,
IT) ; Falchero; Aldo; (Avigliana, IT) ;
Mancina; Guido; (Fino Mornasco, IT) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Family ID: |
39092794 |
Appl. No.: |
12/444269 |
Filed: |
October 4, 2007 |
PCT Filed: |
October 4, 2007 |
PCT NO: |
PCT/IB2007/002953 |
371 Date: |
July 10, 2009 |
Current U.S.
Class: |
407/11 ; 407/118;
407/119; 407/53; 408/145; 409/131 |
Current CPC
Class: |
B23C 2226/27 20130101;
Y10T 409/303752 20150115; Y10T 407/27 20150115; Y10T 407/14
20150115; Y10T 408/81 20150115; Y10T 407/26 20150115; Y10T 407/1946
20150115; B23C 2226/315 20130101; B23C 5/28 20130101 |
Class at
Publication: |
407/11 ; 407/119;
407/118; 407/53; 409/131; 408/145 |
International
Class: |
B23C 5/28 20060101
B23C005/28; B23C 5/16 20060101 B23C005/16 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 9, 2006 |
IT |
TO2006A000724 |
Claims
1-24. (canceled)
25. A milling tool (1, 1') arranged to perform milling while
rotating about a predetermined rotation axis (AR) and including: a
side cutting edge (7, 7'), substantially located on the sides of
the tool (1, 1'); a cutting face (17), on which possible offcuts,
chips and powders produced by the tool (1, 1') are deposited and
flow during machining; a washing channel (11, 13, 11'), which is
formed inside the tool (1, 1') and through which a cleaning fluid
can flow; wherein the washing channel (11, 13, 11') emerges outside
the tool (1, 1') through an outlet hole (15, 15') facing the
cutting face (17) so that the cleaning fluid impinges onto the
cutting face (17) thereby removing from the side cutting edge
possible offcuts, chips and powders produced by the tool (1, 1')
during machining.
26. The tool (1, 1') as claimed in claim 25, including an end
cutting edge (9, 9') located at the front end of the tool (1, 1'),
and an outlet hole (15, 15') facing the cutting face (17) so that
the cleaning fluid impinges onto the cutting face (17) thereby
removing from the end cutting edge possible offcuts, chips and
powders produced by the tool (1, 1') during machining.
27. The tool (1, 1') as claimed in claim 25, wherein at least one
out of the side cutting edge (7, 7') and the end cutting edge (9,
9') is formed on a layer (19) of a cutting material comprising one
or more materials chosen out of the following group: diamond,
polycrystalline diamond, carbides, nitrides, tungsten carbide,
silicon carbide, boron carbide, titanium boride, titanium nitride,
aluminium nitride, cubic boron nitride silicon nitride,
alumina.
28. The tool (1, 1') as claimed in claim 27, wherein the layer (19)
of cutting material is formed by sintering.
29. The tool (1, 1') as claimed in claim 28, wherein the layer (19)
of cutting material is formed by sintering diamond powders having a
grain size in the range of about 2 to about 30 thousandths of a
millimetre.
30. The tool (1, 1') as claimed in claim 28, wherein the layer (19)
of cutting material is formed by sintering on an underlying layer
(21) of tungsten carbide.
31. The tool (1, 1') as claimed in claim 30, wherein the assembly
of the layer (19) of cutting material and the underlying layer (21)
of tungsten carbide is secured to a cutting-insert holder (3) and
the cutting-insert holder (3) is made of a sintered material.
32. The tool (1, 1') as claimed in claim 31, wherein the sintered
material of the cutting-insert holder (3) comprises tungsten
carbide.
33. The tool (1, 1') as claimed in claim 31, wherein the assembly
of the layer (19) of cutting material and the underlying tungsten
carbide layer (21) is secured to the cutting-insert holder (3) by
brazing.
34. The tool (1, 1') as claimed in claim 25, wherein the outlet
hole (15) is arranged to direct a jet of cleaning fluid
transversally of the rotation axis (AR) of the tool (1).
35. The tool (1, 1') as claimed in claim 25, wherein the outlet
hole (15) is arranged to direct a jet of cleaning fluid
longitudinally of the rotation axis (AR) of the tool (1).
36. The tool (1, 1') as claimed in claim 25, wherein the outlet
hole (15, 15') has a diameter in the range of about 0.5 mm to 8
mm.
37. The tool (1, 1') as claimed in claim 36, wherein the outlet
hole (15, 15') has a diameter in the range of about 1 mm to 4
mm.
38. The tool (1, 1') as claimed in claim 25, wherein the side
cutting edge (7, 7') is so constructed that, while rotating about
the rotation axis (AR) of the tool (1, 1'), it describes a cylinder
with diameter DFR, and the outlet hole (15) has a diameter (DFO) in
the range of about 0.04 to 0.4 times diameter DFR.
39. The tool (1, 1') as claimed in claim 25, wherein the outlet
hole (15) has a diameter (DFO) in the range of 0.08 to 0.18 times
diameter DFR.
40. The tool (1, 1') as claimed in claim 25, wherein the number
(NF) of outlet holes (15) arranged to direct jets of the cleaning
fluid onto the cutting face (17) is 0.04 to 0.4 times the length
(LT) over which the side cutting edge (7, 7') extends along
rotation axis (AR) of the tool (1, 1').
41. The tool (1, 1') as claimed in claim 40, wherein the number
(NF) of outlet holes (15) arranged to direct jets of the cleaning
fluid onto the cutting face (17) is 0.08 to 0.18 times the length
(LT) over which the side cutting edge (7, 7') extends along
rotation axis (AR) of the tool (1, 1').
42. The tool (1, 1') as claimed in claim 25, wherein the outlet
hole (15) closest to one end of the tool (1) is spaced apart from
said end by a distance (DEX) that is substantially in the range of
two thirds to a quarter of the diameter DFR of the cylinder
described by the side cutting edge (7, 7') while rotating about the
rotation axis (AR) of the tool (1, 1').
43. The tool (1, 1') as claimed in claim 25, comprising two to
twelve side cutting edges (7, 7').
44. The tool (1, 1') as claimed in claim 25, comprising one to six
outlet holes (15) per cutting face (17).
45. A method of milling a composite material comprising a
reinforcing material embedded in a polymer matrix, wherein the
method comprises the following steps: providing a milling tool (1,
1') as claimed in one or more of the preceding claims; milling the
composite material by means of the tool (1, 1') while injecting a
cleaning fluid into a washing channel (11, 13, 11') formed inside
the tool (1, 1'), so as to remove from a side cutting edge (7, 7')
and/or an end cutting edge (9, 9') possible offcuts, chips and
powders produced during milling.
46. The method as claimed in claim 45, wherein the cleaning fluid
is chosen out of the following group: a liquid, a gaseous fluid, a
gas, a vapour, aerosols, air, nitrogen, an inert gas.
47. The method as claimed in claim 45, wherein the reinforcing
material comprises carbon fibres.
48. The method as claimed in claim 45, wherein the polymeric matrix
comprises an epoxy resin.
Description
FIELD OF THE INVENTION
[0001] The present invention concerns a tool particularly suitable
for milling highly abrasive materials, such as for instance
composite materials formed by carbon fibres embedded in an epoxy
resin.
[0002] The invention also concerns a method of using such a milling
tool.
STATE OF THE ART
[0003] Several criticalities are encountered during chip forming
machining of composite materials comprising carbon fibres
impregnated with epoxy resins.
[0004] Some of such criticalities are related with problems in
cooling the cutting area: the temperature of the composite material
in the cutting area must be kept below relatively low
values--approximately, of the order of 180.degree. C.--to avoid
that exceeding the polymerisation temperature causes burning of the
epoxy matrix, thereby deteriorating the mechanical characteristics
of the composite material. However, cooling the cutting area is
complicated by the impossibility of using lubricants and cooling
liquids, which would pollute the composite material to be
machined.
[0005] Other difficulties are related with the considerable
abrasiveness of the above-mentioned composite materials and of the
powders created, in place of chips, during tool machining: this
causes a quick wear of the cutting edges of the tools.
[0006] It is an object of the present invention to provide a tool,
a device and a method enabling an efficient tool machining of
highly abrasive composite materials, such as for instance composite
materials comprising carbon fibres impregnated with epoxy
resins.
SUMMARY OF THE INVENTION
[0007] According to a first aspect of the invention, such object is
achieved by a milling tool having the features as claimed in claim
1.
[0008] According to a second aspect of the invention, such object
is achieved by a method of milling a composite material having the
features as claimed in claim 21.
[0009] The advantages afforded by the present invention will become
more apparent to the skilled in the art from the following detailed
description of some non-limiting particular embodiments, shown in
the following schematic drawings.
LIST OF THE FIGURES
[0010] FIG. 1 is a perspective view of a first embodiment of a
milling tool according to the present invention;
[0011] FIG. 2 is a cross-sectional view of the tool of FIG. 1,
according to section plane A-A;
[0012] FIG. 3 is a side view of the tool of FIG. 1;
[0013] FIG. 4 is a cross-sectional view, according to a section
plane perpendicular to rotation axis AR of the tool, of a detail of
a cutting insert of the tool of FIG. 1;
[0014] FIG. 5 is a first side view of a second embodiment of a
milling tool according to the present invention;
[0015] FIG. 6 is a side view of the tool of FIG. 5, taken in a
direction orthogonal to that of FIG. 5;
[0016] FIG. 7 shows the tool of FIG. 5 when viewed along the
rotation axis of the same tool.
DETAILED DESCRIPTION
[0017] FIGS. 1 to 4 relate to a first embodiment of a milling tool
according to the present invention.
[0018] Such a tool, generally denoted by 1, includes a
cutting-insert holder 3 having, in the present example, the shape
of an elongated stem. A pair of cutting inserts 5, each having a
side cutting edge 7 and an end cutting edge 9 formed thereon, are
secured to holder 3. Side cutting edges 7 enable side milling by
tool 1, e.g. for contouring and trimming operations, whereas end
cutting edges 9 enable milling by tool 1 while the same is
advancing along its rotation axis AR. That is, tool 1 can perform
both peripheral milling and end milling.
[0019] According to an aspect of the present invention, tool 1 is
equipped with washing channels 11, 13 through which a suitable
fluid, preferably but not necessarily air, can circulate inside
cutting-insert holder 3 and be discharged through multiple outlet
holes 15 located close to and opposite cutting surfaces 17 of
cutting inserts 5, so as to impinge, possibly directly, on said
cutting faces and wash them by jets of compressed air or other
fluids, in order to quickly remove from cutting edges 7, 9 powders
produced during machining. The highly abrasive powders are thus
prevented from quickly wearing and deteriorating cutting edges 7, 9
due to too long a permanence in the spaces between the cutting
edges and the surface of the composite material being cut by the
same edges. Moreover, a finer roughness, or anyway a better surface
finishing, of the surfaces being cut is achieved. Indeed, it is
deemed that the powders worsen the roughness of the surfaces being
cut.
[0020] The cooling and powder removal system operating from the
inside of tool 1 has proven more effective than systems operating
with air jets from the outside, which other companies were
experimenting when the present invention has been conceived and
developed.
[0021] In the exemplary embodiment of FIGS. 1 to 4, a longitudinal
channel 11 and two transverse channels 13 are formed internally of
tool 1. The former extends coaxially with and longitudinally of
tool 1 and rotation axis AR thereof, and the latter branch off from
longitudinal channel 11 transversally of tool 1 and rotation axis
AR thereof. In the present description, channels 11 and 13 are also
referred to as "washing channels". In the embodiment of FIGS. 1 to
4, transverse channels 13 emerge outside tool 1 through four outlet
holes 15 located close to and opposite cutting surfaces 17 of
cutting inserts 5.
[0022] The portion of transverse channels 13 near outlet holes 15,
and the outlet holes themselves, have preferably a diameter in the
range of about 0.5 to 8 mm and, more preferably, of 1 mm to 4
mm.
[0023] Number NF of outlet holes 15 washing a given cutting face 17
is preferably determined according to the following relation:
NF=.alpha.LT (1)
where LT is the length of side cutting edge 7 (FIG. 3) in
millimetres and a is a multiplication factor ranging from 0.04 to
0.4 and more preferably from 0.08 to 0.18.
[0024] Diameter DFO of each outlet hole 15 is preferably determined
according to the following relation:
DFO=.alpha.DFR (2)
where DFR is the cutting diameter of the cutter (FIG. 2), i.e. the
diameter of the cylinder described by side cutting edges 7, under
design conditions, during machining.
[0025] Outlet hole 15 closest to the end of tool 1 is preferably
spaced apart from said free end, along rotation axis AR, by a
distance DEX (FIG. 3) that substantially ranges from two thirds and
a quarter of the cutting diameter of the cutter. More preferably,
such distance DEX is substantially not lower than a third of the
cutting diameter of the cutter.
[0026] The axes of two adjacent outlet holes 15 are preferably
spaced apart by a distance DFS (FIG. 3) that is substantially not
lower than a quarter of length LT of side cutting edge 7.
[0027] Side and/or end cutting edges 7, 9 of cutting inserts 5 are
formed on a layer of cutting material 19 (FIG. 4) that preferably
is polycrystalline diamond--also referred to, in technical jargon,
as PCD (PolyCrystalline Diamond) or PDC (Polycrystalline Diamond
Compact)--or tungsten carbide (WC). Such a layer 19 preferably
comprises synthetic diamond micropowders with a grain size in the
range 2 to 30 thousandths of millimetre. The choice of such a
material and such a grain size results in a significant improvement
to the length of the operating life of tool 1.
[0028] Layer 19 of polycrystalline diamond preferably has a
thickness not lower than 0.1 5 mm and, more preferably, not lower
than 0.4 mm (e.g. a thickness in the range 0.4 to 1.5 mm). Such
layer 19 of polycrystalline diamond is preferably sintered on an
underlying layer 21 of tungsten carbide, and the overall thickness
of layers 19 of polycrystalline diamond and 21 of tungsten carbide
is preferably 0.8 to 3.2 mm.
[0029] Cutting inserts 5 formed by layer 19 of polycrystalline
diamond and layer 21 of tungsten carbide are preferably secured to
cutting-insert holder 3 by brazing, and cutting-insert holder 3 too
is preferably made of tungsten carbide.
[0030] Securing layer 19 of polycrystalline diamond onto substrate
21 of tungsten carbide by sintering and securing cutting inserts 5
to holder 3 by brazing assists in lengthening the operating life of
tool 1. Indeed, such securing systems allow obtaining a more
robust, compact and monolithic assembly, by reducing vibrations and
unwanted movements and making the cutting edges of the tool work in
conditions that better approach design conditions. Moreover, such
systems, by eliminating or substantially reducing gaps and hollows
between cutting inserts 5 and holder 3, if compared to a merely
mechanical system for fastening cutting inserts 5, provide for a
better conductive heat transmission from the outside towards the
inside of tool 1, where washing channels are formed, thereby
increasing the cooling effect of the channels. At the same time,
cooling the polycrystalline diamond, or other cutting material,
improves its abrasion resistance.
[0031] By combining the above features, in particular by combining
washing channels inside the milling tool with the choice of
materials described above, in particular the choice of
polycrystalline diamond as cutting material, the operating life of
a tool 1 could be increased even by 1,500 to 2,000% or more in
comparison to prior art integral, non-cooled tools of tungsten
carbide. Indeed, an operating life exceeding 2 m of cutting length
has never been attained by said prior art tools while meeting
predetermined quality requirements, whereas operating lives even as
long as 40 m of cutting length have been attained by the
above-described cooled tools of polycrystalline diamond according
to the invention. At the same time, by means of a flow of cooling
air the temperature in the cutting area could be kept below
180.degree. C., i.e. below the polymerisation temperature of the
composite material being milled.
[0032] FIGS. 5 to 7 relate to a second embodiment of a milling tool
according to the present invention. In such a second embodiment,
tool 1' has two outlet holes 15' arranged to emit jets of air or
another cleaning fluid towards cutting faces 17', longitudinally of
rotation axis of tool 1' instead of transversally as in the
embodiment of FIGS. 1 to 4. Two washing channels 11', one for each
outlet hole 15', are preferably formed inside tool 1'. Such washing
channels 11' are preferably longitudinally arranged relative to
rotation axis AR of the tool, are as much rectilinear as possible
and are not coaxial with rotation axis AR, whereas washing channel
11 in the exemplary embodiment of FIGS. 1 to 4 is coaxial with
rotation axis AR. The choice of the materials and the system for
securing them onto tool 1' are preferably the same as in the
embodiment of FIGS. 1 to 4.
[0033] The Applicant has realised that a good cooling of tool 1'
and an effective removal of milling powders from the cutting areas
are achieved with such a second embodiment too, even if not so
satisfactorily as with the outlet hole arrangement used in the
embodiment of FIGS. 1 to 4. In the embodiment of FIGS. 1 to 4, the
transverse orientation, relative to rotation axis AR, of the jets
of air or another cleaning fluid discharged from outlet holes 15
seems to make removal of offcuts, chips and powders from the
cutting areas more effective.
[0034] According to a second aspect, the invention concerns a
method of milling a composite material comprising a reinforcing
material embedded in a polymer matrix. In a particular embodiment
of such a method, the reinforcing material of the composite
material consists of carbon fibres and such fibres are embedded in
a matrix of epoxy resin. Such a composite material is milled by
means of tool 1 or 1' described above, by injecting compressed air
into washing channels 11, 13 or 11'.
[0035] Several changes and modifications are possible in the
exemplary embodiments described above, without departing from the
scope of the invention.
[0036] For instance, the number of cutting inserts 5, 5' can
obviously be greater or smaller than two. Other cutting materials,
such as tungsten carbide, silicon carbide, boron carbide, titanium
boride, titanium nitride, aluminium nitride, cubic boron nitride,
silicon nitride, alumina, SiAlON or other suitable carbides or
nitrides can be used in place of polycrystalline diamond.
[0037] Cutting inserts 5, 5' can even be mechanically secured, e.g.
by means of screws or fixed-joint systems, to holders 3 and 3'. In
this respect, it will be appreciated that, in the present
description, the term "cutting inserts" includes cutting bodies
secured to a cutting-insert holder not only by brazing, soldering,
sintering or gluing, but also by reversible or irreversible
mechanical systems, or other different securing systems. Nitrogen,
other inert gases or, still more generally, suitable gaseous
substances, such as gases, vapours and aerosols, or yet liquid
substances can be used in place of air as washing fluid. Clearly,
still further modifications are possible.
* * * * *